Energy-saving lamp is also called compact fluorescent lamp, the advantages of which are high lumen efficiency, low power consumption, long useful life and compact structure, etc., thereby it has been widely used. As shown in FIG. 1, a normal energy-saving lamp comprises a burner 1 and a lamp base assembly 2, wherein the burner 1 is mounted on the lamp base assembly 2, and electrically connects with the lamp base assembly 2 by a leaf spring 11. The lamp base assembly 2 includes a housing 22, a lamp cap 21 mounted on one end of the housing 22, and an electronic ballast 24 mounted within the housing 22. The circuits of the electronic ballast are commonly used in the form of saturated magnetic toroid (current drive) circuit, MOSFET circuit, and voltage drive circuit with bipolar transistor (no magnetic toroid). In the above three kinds of circuits, the first two circuits are of high cost. Therefore, in the low-cost electronic energy-saving lamp, the voltage drive circuit with bipolar transistor, in which one or more bipolar transistor 23 are contained (hereafter referred as transistors 23), is usually used. However, one disadvantage is, within the desired scope of supply voltage and operating temperature of the energy-saving lamp, the temperature of the transistors can not be kept within a safe scope; as a result, the lifetime of the whole energy-saving lamp will be shortened. Therefore, lowering the temperature of the transistors becomes a problem to be solved in the prior art.